Train control



' C. S. BUSHNELL TRAIN CONTROL Filed Jan. 6, 1922 2 Sheets-Sheet 1 fi A TTORNE Y.

2 Sheets-Sheet 2 C. S. BUSHNELL TRAIN CONTROL Filed Jan. 5, 1922 0+ n ma July 13 1926.,

flTTORNEY.

Lo c P Patented July 13, 1926.

' UNITED. STATES PATEN OFFICE.

cHAnLns s. BUSHNELL, or aocnns'rnmNnwvonx, ssIGNonro GENERAL BAIL- wAY sIeNAL COMPANY, or eAT'ns, NEW YORK, A CORPORATION or NEW Yomz.

.- TRAIN coN'rnoL.

Application HIed'J'anuary S, 1922. Serial No. 528,556.

This invention relates to cab signal ortrain control systems, and particularly to means for transmitting acommunicating ingutinee from the trackway to'a m0vingve- In cab signal and train control systems, it is necessary to communicate control in-, fluences from the trackway to a moving train under dangerous traffic conditions, such as an occupied block or crossing, open siding, or the like, such communicating influences being received on the vehicle by suitable mechanism, which will automatically slow down or stop the train or impose some other form of control., It is considered desirable to establish such communication between the traekway and moving vehicles inductively,- rather than by physical'pontact between mechanism on the vehicle and devices along the track. On account of the clearances re quired between devices on the vehicle with respect to the track and devices onthe track with respect to rolling stock of'all kinds, including snow flan'gers,suc h inductive communication must take place through a rela-:

tively large air gap when the track elements are between the track rails, and this air gap will reduce the magnitude of such communicating influences considerably.

Also, in one type of system to which this invention is more particularly a'daptable,the stopping influence is produced on the car on account of the magnetic nature of the track element; and since the track rails at switches and crossings, and like magnetic bodies along the track, will tend to produce an effect upon the car apparatus similar to that of the track element, there is a difficulty encountered in this type of system, conveniently termed rail interference, that necessitates speciahprovision to distinguish between the,

effects of the regular track element in its active stopping condition and the effect of track rails. and the like. One remedy for this difliculty is to provide a construction. of trackelement that is capable of producing a magnetic effect quite different from any or.- ganization of track rails orother magnetlo bodies ordinarily encountered along the track, so that the car apparatus is able to effectively differentiate, so to speak, between the magnetic loop orpartial circuit afi'ol'dcd by the track element and that afforded by the track rails; a

Tith the above and other. considerations in mind.. the principal object and purpose of the present invention is to accentuate the influencein an inductive communicating system of this kind, without expensive addition or duplication of parts, by superimposing a plurality ofsuccessive influences upon the same car-carried apparatus in a manner wherebyvthe eftect ofsuch influences will be cumulative, and will occur in a relation not: likely to be produced by track rails or other magnetic bodies along the track. Other objects and purposes of the invention will appear as the description protraincontrol system employing the presentinvention Fig. 4 shows graphs or curves of. the voltages induced due to a change of flux in the several magnetic circuits of the car-carried element; Fig. 4 shows a curve of the resultant voltage due to the voltages graphically illustrated in Fig. 4;

Fig.'5 is a circuit diagram of a modified form of train control embodying the present invention; and

Fig. 6 is a plan view of the car element illustrated in Figs. 3 and 5.

In-the embodiment of the invention illustrated, the transmission of the desired controlling influences is produced by track elements which are governed in accordance with traffic conditions. Various arrangements of trackway circuits suitable for this purpose maybe employed, and it is to be understood that the arrangement shown in Fig. 1 is merclyillustrative. Referring to Fig. 1, the track rails l of the railroad track are divided by insulating joints 2- into blocks in -the usual way, one block I with the adj aeent ends of train control a paratus; and trated such fixe of two other blocks H and J being shown. The parts and circuits associated with the various blocks are the same, and for convenience will be given like reference charactors with distinctive exponents. Each of the blocks is provided with a track battery 3 and a track relay 4, the same as in the ordinary block signaling systems. My invention may be used with or without the elements T and U, each comprising a U- shaped core 5, referably laminated, and provided with en arged pole pieces 6. Each core 5 has a coil 7 on each of its legs; and

these coils are wound and connected in series so that the electro-motive-forces generated in tbesecoils 7 by a change of flux through the core 5 are cumulative or additive. One of the legs of the U-shaged core 5 of-each track element is prefera ly slightly longer than the other (see Fig. 3), for purposes to be explained hereinafter. Thea track elements T and U are mounted substantially parallel to each other and crosswise of the track in a manner to bring the adjacent pole pieces 6 of the longer legs substantially 1n the center of the track as illustrated.

These traclrway elements. T and U produce and transmit controlling influences or impulses to a passin train at one orgmore control hits in eac block, in accordance with tra 0 conditions in .the next block in advance alone, or boththe next block in ad,- vance and the corresponding block, depending upon the type of traincontrol appa ratus employed. :1 the trackwa y equipment illustrated in Fig. 1, a pair of trackway ele-' ments T and-U are located at the entrance to each block, a short distance inwthe rearof insulated joints 2, the normal direction of trafic being from left to ht as indicated by the arrow. The coils of each of the trackway elements '1 and U are connected in series in aparate normally closed circuits including the front contacts Sand 9, respectively, of a line'relay 10. In the ar-' rangement ilhntrated, the control circuit for the line relay 10 includes a front contact 11 of the track relay-4 of the corres ndi block, and a front contact 12 of t e trac relay 4 of the next block in advance, so that the coils 7 of the trackway elements T and U at the entrance to each block are in a closed. circuit of preferably low resistance under clear trafiic conditions, but are open-circuited when either the corresponding block or the next block in advance is occupied.

The car element L for-coo crating with the track elements T and U igs. 2, 3 and 6), com rises a yoke Y having three vertically disposed legs 13, 14 and 15, each havi% an enlarged pole piece? This yoke, w ich is pre erably ma e up of soft iron laminations,'is supported in a suitable manner (not shown) from the locomotive or other vehicle and is so positioned on this vehicle that two of its legs, such as 13 and 14 which are s aced apart the same distance as the legs 0 a track element, will pass directl 'over' the two legs of the track element 1%, while the le s14 and 15 will pass directly over the two% element U. The manner in which the car element L maybe sup rted will vary accordingxto the type oi locomotive or car, and it as not been attempted to show any particular construction for this purpose. In the case of the ordinary locomotive aconvenient place for the car element L is found in front of the pony truck; and in all cases it is desirable to keep the pole pieces of the car element as far away from any iron parts of the engine frame as possible. The car element'L with its coils will in practice be inclosed and protected in a casing of suitable non-magnetic material.

The car element L and the track elements T and U are disposed so as to make the air gap between their 'pole pieces as small as possible, consistent with the roadway and equiipment'clearances 0n the particular railroa On certain railroads the-fiangcrs of the snow plow extend considerably below the top edge o'f'the rail between the rails of the track, but .need not extend necessarily along the entire distance between the rails,

because ,the middle portion of the space between the rails need not be lowed out lower than the top edge of the ralls. This may be done bynotching out the middle part of the flanger; and for systems of this kind those legs of the track elements disposed midway between the rails may extend u to substantially the top of the rails as 1 lustratedin Fig. 3, thereby im roving the air gap-to the extent permissible under in conditions on such roa s.

the two outside 1e? 13 and" 15 of the car element L, shown in ig. 3, are two coils coils, which are wound with the same num' ber of. turns, and are connected together in an energized circuit, so that they will create opposing magneto-motive-forces tending to send -flux in the same direction in the back yoke Y and outside legs 13 and 15, and in the o posite direction in the middle leg. 14. uttingit another way, if the coil 16 egs of the other track ill) ractical work- 16 and 17 conveniently termed primary.

. other coil 17 ma es a south pole at its pole' makes a north ole at its pole piece, the

piece, and the magneto-motive-force exerted in the middle leg 14 by one of these coils Wlll be counteracted by the magneto-motiveforce exerted by the other coil.

Since the impulse transmitting means- While the E. P. V. may be made so as to be directly responsive to the inductive control influences transmitted by magnetic cooperation of the car-carried and trackway elements, I consider it preferable in most cases ,to employ a control relay R for governing said E. P. V. This relay R is of course constructed to have operating characteristics conforming with its use; but since these features form no part of the present invention, this relay has been ilin order that the wor ing current for said v relay may be larger and the relay made lustrated conventionally.

It may also be made directly responsive to the inductive control influence, it is considered preferable While the control relay to employ an amplifying device responding to the influence for overning said relay,

more substantial and reliable in construe-- tion. For this purpose an amplifier of the thermionic or vacuum type, commonly known as an audion, is employed. This audion, being well-known in the electrical art, isillustrated conventionally and comprises a filament F, a grid G and a plateP.

This audion and the other parts are con nected up with suitable sources of current illustrated as batteries A, B, and C. Gen-' erally speaking, the secondary coil 18 of the car element L, the audion, and the control relay R are so connected in the system that the front contact 19 of the relay will open as the car passes over the pair of track elements T and U in their active stopping condition. The electrical connections" of these devices may takev various forms and the articular arrangements shown are more typical and have been illustrated so that t e operation of the communicating device may be explained. 9

Referring to Fig. 3, the filament F of the audion is heated by ,a battery A. The

grid G is connectedin circuit with the. secondary coil""18 and the battery B, so that a positive potential with respect to the negative end or average potential of the filament is normally maintained; Thisgrid circuit .may be traced' as follows :-beginning at the positive terminal of the battery B, wire 27, secondary coil 18, wire 28, grid G to the filament of the audion, back to the negative terminal of the battery B. This permits current to flow in the plate circuit through the relay R, as' follows beginning at the positive terminal of the battery C, wire 29, front contact 19 01? the control relay R wire 30, wire 31, winding of the control rela R, wire 32, plate P of the audion to tie 'filament F, and back to the negativeterminal of the battery C. The primary coils 16 and 17 are connected in serieswith the E. P. V.v and are energized by the batteries B and G in a circuit which may be traced as follows beginning at the positive side of the battery C, wire 29, front contact 19 of control relay R, wire 30, wire 33, contact 21 of reset switch RS, wire 34, wire of the train control device E. P. V., wire 35, prlmary coil 17, wire 36, primary coil 16', wire 7 37, and back to the negative terminal of the battery G. The primary circuit is controlled by the-front contact 19 of the relay R, the relay R- being connected in the plate circuit of the audion through the batteries B and C and through the front contact 19 of the relay R, thus making this-relay a stick relay, which, if momentarily opened, will remain open until it is again 'reset. For the purpose of resetting this stick control relay B after it has been deenergized,

a reset switch RS has been provided which comprises a push button or double throw switch blade 20 cooperating with stationary contacts 21 and 22 in a manner such that the circuit through the E. P. Vxwill be broken when the front contact 19 of therelay is shunted by pushing the button 23 of this reset switch RS. The advantage of this form of reset switch makes it impossible for the engineer topprevent the actuation of the E. P. V., by holdin .or'

fastening down the reset switch .to. s unt the front contact 19 of the control relay B, because when the switch is operated to shunt said front contact, the circuit through the E. P. V. will be broken at the contact 21, thus eflecting an automatic stop or other form of control.

When the car is traveling between the track devices under normal clear traflic con-' ditions, the relay R is energized, and in turnmaintains the train control device E. P. V. energized. The current in the primary coils 16 and 17 tends to send flux through the yoke Y and across the space between the outsidelegs 15 and 16, there being little, if any, flux passing throughtwo legs 13 and 14 of the yoke Y, thus causing a change of flux through these legs and inducing in the secondary coil 18' one cycle of voltage, as shown by the graph or curve 24in Fig. 4, the portions of the curve above the line being taken as positive and thus adding to the voltage of the battery B,

. whereas the portion of the curve below the line represents a negative voltage opposing the voltage of this battery.

'.-"When the car element L passes over the other track element U, a corresponding voltage 'will be induced in the secondary coil 18 which will be in the opposite direction to the first cycle of voltage induced, because the voltage in the second instance is due to the flux produced by the pole 15, which is of opposite polarity to the pole 13 which pro duced the first change of flux. The distance between the track elements is properly chosen with due regard to varying conditions found in practice, so that the second part or negative portion of the first curve 24 will be substantially in phase with the first part or negative portion of the second curve 25, thus inducing a resultant voltage in the secondary coil as illustrated by the curve 26 in Fig. 4. The negative portion of the curve 26, shown in Fig. 4*, comprises the summation of portions of the curves illustrated in Fig. 4, and the middle downwardly projecting portion of this curve represents a voltage double that represented by the first and last portions of this curve, which first and last portions represent the voltages of single waves. These curves are only'representative, and are not to be accepted as accurate for every condition. This reduction of potential on the grid G of the ..a-udion produces a magnified reduction of the plate current of the audion passing through the relay R. The deenergization of the plate circuit causes the armature and front contact 19 of the control relay R to drop, thereby opening the circuit through the E. P. V.

The dcenergization' of the train control valve E. P. causes the train to be automatically slowed down or brought to a stop in a manner dependent upon the particular kind of train control apparatus used. To restore the relay R and reset the train control valve E. P. V., it is necessary to push the button 23 of the reset switch, which will establish the following circuit z-beginning at the positive terminal of the battery C,

' wire 29, wire 38, contact 22 of the reset switch RS, wire 83, wire 31, winding of the control relay R, wire 32-, plate P of the train control apparatus illustrated in Fig. 3

in a normal condition as shown, is moving inthe direction of 'the arrow and.is approaching the entrance of the block I; and assume further that there is no train in block I or J so that the line relay 10 is energized and hasits front contacts 8 and 9 closed, thus including the coils 7 of track elements T and U in closed circuits of low resistance. If now the car element L passes over the track elements T and U, no control influence will be transmitted. This is believed to be due to the fact that, a bucking or demagnetizing current is set up in the coils 7 of the track elements T and U, due to a slight increase of flux which will set up a counter-magneto-motive-force tending toprevent a further increase in flux, this slight change of flux being insufiicient to generate sufiicient E. M. F. in the secondary coil 18 to drop the armature of the control relay R. 'Thus, the track elements T and U are ineffective to transmit a control influence when in their normal condition, that is, with their coils 7 in closed circuits of low resistance.

\Nhenever the car element L passes over magnetic bodies, such as switch points, crossing rails and the like, it is found that no appreciable, if any, voltage will be induced in the secondary coil 18. According to one theory, this may be attributed to the fact that the shortest path for the magnetism will be through the yoke, its outside legs and the crossing rail, so that there is no change in flux through the secondary coil 18 on the middle leg 14.- If the crossing rail or switch point should make an acute angle with respect to the track, the rail would bridge the middle leg and one of the outside legs beforev it would bridge the middle leg and the other out-side leg, thus tending to cause an unbalancing of the opposing magncto-motivc-forces in the middle leg 14, due to a difference in the reluctance of the two partial magnetic circuits through said leg occasioned by the switch point or crossing rail; and such unbalancing causes a change in flux through the secondary coil 18, affecting the grid potential, and dropping relay R. with the result that a harmful and false impulse may be transmitted under unfavorable conditions.

In order to obviate the possibility of such a false influence, the outside legs 13 and 15 of the track element are preferably provided with extending pole pieces 39 and 10, preferably made up of soft iron laminations. These pole pieces, which have been shown broken away in Figs. 3 and 5 to avoid confusion, may take various forms, but are preferably of arcuate shape, as illustrated in Fig. 6. If a car element L, pro-' vided with arcuate extending pole pieces of this kind, passes over a crossing track rail making an unfavorable angle with respect to the track, changes in reluctance will take place simultaneously in the two outside legs of the car element L, the shortest path for the flux being through the yoke, outside legs, extended pole pieces and the crossing rail, so that very little, if any, change of flux will occur in the middle leg, thus inducing little, if any, voltage in the secondary coil 18 and therefore not causing a false operation of the car-carried apparatus. Or, in other words, the extended pole pieces 39 and -10 facilitate a magnetic path of low reluctance through both primary legs when a crossing rail of substantially any angle with respect to the track rails is encduntered. providing a )ath of low reluctance which does not include the leg'14 or the secondary coil 18, that is, when the two partial magnetic circuits are simultaneously completed the resultant electro-motive-force induced in the secondary coil 18 is substantially zero.

In Fig. 5 the e has been illustrated a modified form of car-carried apparatus illustrated in Fig. 3. The cooperative track devices for this embodiment of the invention are the same as shown in Flgsjl, 2 and 3. The general circuit arrangement of'this embodiment of the invention is substantially the same as in Fig. 3, and like parts have been designated by the same reference charaoters. The main differences in structure between this modified arrangement and the embodiment of Fig. 3 is that a primary coil 16 on the middle leg 1% has been substituted for the primary coils 16 and 17 on legs 13 and 15, respectively; and that two secondary coils 18 and 18 located on the legs 13 and 15 and connected by a wire 18 have Although the general circuit arrangement of this particular form of my invention is very much like that shown in Fig. 3, the theory and principle of operation is believed to be quite different. Assume that the track elements T and U are in their stopping or danger condition, that is, with the coils 7 on the legs thereof open circuited, and that the car equipped as illustrated in Fig. 5, with thetrain control valve E. P. V. energized and with the apparatus otherwise in its normal condition as illustrated, travels past these track elements. As the car element L passes over the track element T, said track element reduces the reluctance of the magnetic path through legs 18 and 1 1 of yoke Y, thus inducing an E. M. F. in the secondary coil 18 as shown by the solid curve 24 in Fig. 4, and as the car element L passes over the track element U, a voltage is generated in the secondary coil 18 in a similar manner, as represented by the dotted curve of Fig. 4.

It will be noted that the first Wave of the voltage induced in the secondary coil 18 is positive, while the first wave induced in the secondary coil 18 is negative. This is due to the fact that these coils are wound and connected oppositely as above explained. The resultant voltage due to these two induced voltages is shown by the curve 26 in Fig. 4 and the secondary coils 18 and 18 are so connected in the grid circuit that the negative or downward wave of the voltage curve 26 opposes the voltage of the battery B, this negative voltage being of sufficient magnitude under predetermined operating conditions to buck or oppose the voltage of battery B to suchan amount that the control relay R will open its front contact 19 and dccnergize the train control valve E. P. V., and thereby control the train in any suitable manner as heretofore explained.

When crossing rails are encountered disposed crosswise of the track rails, no resultant voltage will be induced in the secondary or grid circuit to oppose the voltage of the battery B, because the slight voltages induced in the secondary coils 18 and 18 due to the change of reluctance caused by the track rails will be equal and opposite. It is apparent that crossing rails making an acute angle with the track rails will induce voltages in the secondary coils 18 and 18 which may, under certain adverse circumstances, not be induced simultaneously and therefore will not fully oppose each other,

thereby tending to cause a false stopping control. In order to bring these voltages in time phase relation or induce them simultaneously, extended pole pieces 39 and 40, as illustrated in Fig. 6, are preferably used. These extended pole pieces 39 and 40 cause the reluctance of both magnetic paths through the secondary coils 18 and 18 to be changed simultaneously as the car element L passes over such rails making an acute angle with the track rails. The effect of these extended pole pieces is similar to that described in connection with the first embodiment of the invention.

This invention provides an influence communicating or transmitting means for train control systems embodying a car-carried element which receives one form of influence when approaching a track element, and another form of influence when receding from a track element, and. in which the approaching influ nce of a track element disposed in a particular relation to the car element will be in the same direction as the receding influence due to another track element disposed in a different relation to the car element, thereby forming a plurality of infiuences received in the proper time phase relation to be cumulative. Also, the plurality of influences received from track rails disposed at an angle to the trackway are not cumulative but opposed in character.

\Vith regard to the problem of rail interference characteristic of the type of influence communicating means employing an inert unenergized track element, it will be appreciated that the track element can in practice be made a much better magnetic conductor than the switch points, crossing rails, water pans, and other bodies of magnetic material ordinaril encountered along a railroad track. T e track elements, howi ever, when located between the track rails,

have to be kept down below the level of the track rails at least, so as to be out of the way of the rolling stock; and if it is required to have these track elements clear of the flangers of snow plows, the track elements must be kept some distance below the level of the top of the track rails. Consequently, under the practical working conditions ordinarily encountered in practice, the track rails of crossings, switch points, and the like will be closer to the car-carried element than the cores of the track elements, and will have an advantage of a smaller air gap in changing the reluctance of the partial magnetic circuits of the car element.

Another factor is that the car relay R is preferably dropped by the track elements with an ample margin to take care of variations in battery voltage, changes in the air gaps due to wheel wear, changes in resistance of the several coils or windings due to temperature variations, and so on; and while the track element should always cause operation of the relay under the most unfavorable conditions of battery voltage, air gap, and the like, likewise the switch points or track rails of crossings should not cause operation of the relay under the most favorable conditions of air ga and the like; otherwise there is a possibility of an improper or premature operation of the relay when conditions are such to favor its operation by the track elements as well as by switch points and the like.

On account of these variable factors, it will be evident that the problem of rail interference resolves itself, so to speak, into the problem of making the regular track elements of the system as effective as possible when compared with the rails of crossings and switch points; and it will be evident that there is considerable difliculty in doing this where it is attempted to keep all parts of the track elements down close to the top of the ties so as to clear the flangers of snow plows, many railroads apparently seriously objecting to raising the flangers at each track element. This difficulty is partially cured if, as previously explained, th snow flangers are notched or cut out for a Iew inches in the middle of the track, where an accumulation of snow and ice is not so objectionable, so that the legs and pole pieces of the track elements may be brought up at this point approximately on a level with the top of the rails, it being obvious that this expedient reduces the air gap between the car element and the track element on one side.

This specific arrangement is the one shown in the accompanying drawings; but is should be understood that the invention is in nowise limited to this particular arrangement, and that the outside legs of the track elements may also come up to the level of the top of the rails, or even above if the prac tical working conditions and the requirements of the railroad permit.

It might be added that arrangements of the track elements other than that shown may be employed, the car apparatus of course being modified accordingly. For example, if desired, the track elements may be located one inside of the rail and the other outside, or both outside of the rails, disposed either crosswise or lengthwise of the track so long as the relative spacing, or the points of cooperation between the car-carried and trackway partial circuits, are made in accordance with this invention, so as to produce two overlapping unicyclic impulses.

From the foregoing discussion in regard to the problem of rail interference, it will be appreciated that material advantages is obtained in widening the margin for a safe and reliable operation, if the influence produced between track elements is increased with respect to the similar influence that any track rail or switch point will be able to produce under like conditions of air gap,

batterv voltage and the like.

According to this invention, this desirable end is obtained, as previously explained, by

providing a combination or arrangement of partial magnetic circults of the trackway in a lll spaced relation so as to produce overlapped waves, as shown in- Fig. 4*, with the result that the voltage change causing operation of the car apparatus and produced by the track elements is much greater, perhaps even double, than that which can be produced by a track rail. gap between the track rail and car element is less than that between the track element and said our element, the difference in the magnitude of the influences produced, respectively, by the track rail and track element results in a safe and ellcctive operation of the relay under most unfavorable conditions when the train passes an active group of track elements, while the relay is not operated under mostfavorable conditions by a switch point or track rail of a crossing.

It should be. noted that the spacing ot' the track elements T and U is of course made much shorter than the track gauge, so that the two rails of a crossingwill not produce the successive influences necessary to obtain the same. etl'ect as the two track elements. in short, in accordance with this invention,

the track elements in cooperation With the car apparatus produces a distinctive and accentuated etl'ect, specifically two overlapping unicyclic voltage curves, this effect being one which can not be obtained from any arrangement or combination of track rails or other magnetic bodies ordinarily found along a railroad track. It is on account of this marked difl erentiation in effect that, if desired, the elongated pole pieces 39 and 40 shown in Fig. (3 may be omitted where the working conditions are otherwise organized to provide the necessary margin of operation between the influence of the regular track devices and the track rails.

The specific constructions and arrangements of circuits shown and described are merely illustrative of the invention, and do noteshaust the various modifications and adaptations that will perform the same function and have the same mode of operation. Many changes of this character will be evident to those skilled in the art and need not be specifically shown or described. For example, any well-known or suitable form of trackway circuits, or even manual control, may be employed for governing the control circuits of the track elements; and while the coils 7 of these elements are shown as included in separate closed circuits, with the icw of reducing the external impedance of the circuit for each pair of coils. a single circuit with the two pairs-,ol coils in series may be used to ad vantage in many instances. Likewise. while the relay ll is shiprn as a stick relay. it may be so connected asto open its contacts only momentarily. thedesired prolongation of control being obtained by a stick relay or imilar device governed by said relay R. Such devices, as well as the Consequently, although the air stick relay R- shown in the particular arrangement illustrated, may, if desired, be reset or restored automatically instead of by hand. The train control apparatus itself, represented in a simple form by the electro-pneumat-icvalve E. P. V., may take various forms, in'iposing the desired control or regulation of the train.

Also, it will be recognized that the various adjuncts, such as cab signals, provision for reversal of the locomotive or vehicle, control for interlocking territory, and so on, may be used in connection with the system illustrated. In fact, it is appreciated that this invention may be. practiced by a large number of variable forms of specitic apparatus and circuits, using alternating current instead o'l direct current, modifying the harm or shape of the cores, reorganizing the car circuits, and so on; and I desire to have it understood that 1 consider the invention to be generic in its scope and utility, and in no sense restricted to the specific embodiment illustrated and minor deviations there from.

What I claim is 1. In a train control system, the combination of a plurality of trackway influence creatingdevices for producing successive influences each having a positive and neg-a tive value so spaced that the second influence of the tirst element occurs at. the same time as the first influence of the second element, and car-carried apparatusincluding an electro-responsivc device having an armature associated therewith which armature responds to the accumulative eflect of said.

influences.

2. The combination of trackway influence creating means for train control and cab signal systems, comprising, a plurality of track devices each creating an approaching and receding influence, said track devices being spaced so that the receding influence of one will become eti'ective as the approaching influence ot" the other becomes etlective, and of car-carried apparatus including an electro-responsive device having an armature which responds to the accumulative etiect of said last mentioned receding and a1. proaching influences.

2-5. A. train control system comprising, a car-carried influence receiving device having a primary and a secondary circuit. and trackway means for ljn'oducing a plurality of cycles of. R. M. l. in said secondary circuit in such a manner that portions of said .ll. hi. F. are cumulative. I

4. To a train control system. the combination of a car-carried (lc\ice for receiving: control influences from the trackway. and traclrway means for producing a plurality of appromhin; and recedin; influences in the car-carried devices when passing theicovel', said influences being so related that a receding influence and an approaching influence are cumulative, and means actuated by said car-carried device for restricting the speed of the train upon the reception of a cumulative influence.

5. In a train control system, the combination of a. car-carried device for receiving control influences from the tracltway, and a tlilCl("21 Y influence creating means for producing a plurality of approaching and receding influences in the car-carried devices passing thereovcr, said influences being so displaced with respect to the position of the vehicle as it moves along the track so that secondary winding from a maximum 1n one direction to a n'iaximum in the other direction when said element passes over said trackway means.

7. In a train control system for vehicles running along. a trackway, of trackway means for transmitting successive o verlapping control influences, and car-carried apparatus including a car element adapted to be actuated upon the reception of overlapping influences, but. ineffective to said in: fluences when transmitted simultaneously.

8. Connnunicatingdevices for train eontrol systems comprising, a plurality of track elements located in ditlerent paths along the trackway and spaced :1 distance apart to reduce overlappinginfluences. each of said influences comprising an increasing mag netic flux followed by a decreasing magnetic flux, and car-carried apparatus including a secondary coil afl'ected oppositely by said influences, whereby a cun'iulative efl'cct will be; produced upon said apparatus.

9. An automatic train control system comprising. a train control device, car-carried means for initiating said train control de-' vice including a secondary circuit, an electro-responsive device in said circuit having an armature associated therewith and a plurality of trackway devices acting cumulatively to actuate said armature when said car-carried means passes by said trackway devices.

10. Influence transmitting means for train control systems comprising, a car-carried element having a plurality of partiallmagnetie circuits, means associated with said partial magnetic circuits responsive to a change of flux through either of said magnetic circuits, and a plurality of trackway devices located along the traclrway in a mannner to cause a cumulative influence to be transmitted by said plurality of devices when said car-carried element passes over said dcvices.

l1. Influence transmitting apparatus for automatic train control systems coi'nprising car-carried apparatus including an elcctr0-' responsive device connected in circuit with a. secondary coil, and means including spaced trackway devices for changing the flux from a maximum in one direction to a maximum in the other direction through said secondary coil, whereby the cumulative effect of said trackway devices causes actuation of said electro-responsivedevice during the passageot said car-carried apparatus over said trackway devices.

12. Influence transmitting apparatus for automatic train control systems, comprising, a car-carried element of magnetic material having three legs, sources of uni-directional n1agi1eto-motivefoi'ce associated with two of said legs, and independent t-raclrway devices t'or successively bridging the two airgaps formed by the three legs of saidcae carried element. VI

13. An automatic train control system comprising; a normally energized stick relay connected in series with a source of energy in a stick circuit, an eleetro-responsive device govern ng said relay. and means including a plurality of traclrway devices for cuimilatively inducing a voltage acting upon said device to cause. momentary deenergization of said relay, whereby it will be permanently deenergized due to interruption of said stick circuit.

14. In an automatic train control system. the combination with car-carried apparatus including a thermionic device, and a relay controlled thereby, and of trackway means comprising a plurality of track elements adapted to cumulatively afl'ect said device to cause deenergization of said relay when said car-carried apparatus passes by said traclrway devices.

15. Influence transmitting apparatus for automatic train control systems comprising, 'ar-carried apparatus including a secondary coil and a plurality of sources of magnetomotive-force, and trackway devices for alternately directing flux from one and then the other of said sources of magneto-motiveioree through said secondary coil.

16. In an automatic train control system. the combination of car-carried apparatus comprising, a circuit including an electroresponsive device. a car element of magnetic material having two partial magnetic circuits, and means associated with said car element to cause voltages to be induced in opposite directions in said circuit when one of said partial magnetic circuits is magnetically bridged when the other is brid ed, whereby simultaneous bridging of t ese partial magnetic circuits causes the volta es to neutralize each other and alternate bri ging of these'partial magnetic circuits causes a cumulative Volta e to be induced in said circuit, and of trac way elements for alternately bridging the partial magnetic circuits during the passage of the car element over the trackway elements.

17. An automatic train control system according to the preceding claim, wherein the car element is provided with extending pole pieces, whereby a long magnetic body will bridge both of said partial magnetic circuits simultaneousl regardless of the angular disposition 0 said magnetic body with respect to the trackway.

18. In a train control system the combination with a car-carried element comprising, a core having three legs, two of said legs. having horizontally extendin pole pieces, whereby a long magnetic bo will brid e both of said partial magnetic circuits simu taneously re ardless of, the angular disposition of sai magnetic body with re spect to the trackway, and trackway elements for alternatel bridging one pair and then another pair 0 said legs.

19. A train control system, comprising a car-carried influence receiving element including a core having three legs, two of said legs having pole'pieces extending horizontally on opposite sides of the third leg, whereby a long magnetic body will bridge both of said partial magnetic circuits simultaneously regardless of the angular dispocomprising, a core having a receiving coil operatively connected to said relay, two opposing sources of magneto-motive-force as sociated with said core, both tending to send flux through said receiving coil, and trackway elements controlled in accordance with traflic conditions ahead which when active are capable of alternately reducing the reluctance between one and then the other of said sources of magneto-motive-force and said receiving coil.

. 21. A train control system according to the preceding claim, wherein the track elements are so spaced along the trackwa that the flux through said receiving coil ue to one of said sources of magneto-motive-force decreases simultaneously with the increasing flux due to the other source of magnetomotive-force.

In testimony whereof I hereto ailix my signature.

CHARLES S. BUSHNELL. 

